The present invention relates to a device and a method for influencing the propulsion of a vehicle.
German Published Patent Application No. 1 902 944 concerns a control device for preventing motor vehicles from skidding during cornering. The motor vehicle contains an antilock braking system, measuring elements which measure the driving condition, and final control elements which are controllable via the measuring elements. The measuring elements include gyroscope, wheel sensors, steering sensors, and potentiometers. The measuring elements are connected to a programmed control unit which responds to limiting values of the transverse acceleration of the vehicle. The final control elements for controlling the braking system and a power-controlling element of an internal combustion engine can be tripped via the control unit for directional stability. The directional stability device becomes active already below the maximum permissible transverse acceleration for the intended vehicle design so that the vehicle cannot get into an unstable driving condition. It is believed that there is no provision for making allowance for a variable describing the time behavior of the transverse acceleration.
An object of the exemplary embodiment and/or exemplary method of the present invention is to improve existing devices or methods for influencing the propulsion of a vehicle to the effect that the time or dynamic response of the vehicle is also allowed for in the influencing of the propulsion.
The exemplary embodiment and/or exemplary method of the present invention is directed to a device and/or a method for influencing the propulsion of a vehicle. The device includes a first apparatus, arrangement or structure which is used to measure a transverse acceleration variable describing the transverse acceleration acting upon the vehicle. According to an exemplary embodiment of the present invention, the device contains a second apparatus, arrangement or structure which is used to determine a variable describing the time behavior of the transverse acceleration variable. Moreover, the device has a third apparatus, arrangement or structure which is used to determine an intervention variable at least as a function of the transverse acceleration variable and of the variable describing the time behavior of the transverse acceleration variable. Furthermore, the device features a fourth apparatus, arrangement or structure which is used to carry out or perform at least engine interventions for influencing the propulsion, the engine interventions being carried out as a function of the intervention variable.
It is advantageous for the intervention variable to describe the throttle-valve angle to be adjusted, or the fuel injection quantity to be injected, or the ignition point to be adjusted. If the vehicle is equipped, for example, with an Otto spark ignition engine, then the throttle-valve angle or the ignition point (ignition angle) may be used as the intervention variable. In the case of a vehicle equipped with a diesel engine, the fuel injection quantity is usable. Ignition interventions permit a quick reduction of the engine torque.
The exemplary method according to the present invention can also be used for vehicles which are equipped with an electric motor. In this case, the electric current flowing through the motor is to be regarded as the intervention variable.
In addition to the engine interventions, it is also believed that it may be advantageous to carry out or perform interventions in the wheel brakes and/or in the clutch and/or in the transmission for influencing the propulsion of the vehicle. By appropriate interventions in the wheel brakes, the vehicular speed may be reduced. By interventions in the clutch, the drive train is opened for a short time as a result of which the driven wheels, being free from longitudinal forces, are able to transmit the maximum lateral force. As an intervention in the transmission, it is conceivable, for example, to shift up one gear to reduce the drive torque. The influencing of the propulsion torque can give rise to a limiting of, a reduction of or an increase in the propulsion torque.
The intervention variable is believed to be advantageously determined in such a manner that the vehicle is stabilized in the transverse direction by the engine intervention. Via the engine intervention and further interventions described above, the vehicle stability is influenced at the limit, thus supporting the driver in critical driving situations. In the propulsion case, the steerability of the vehicle is increased, the vehicle tends to understeer less strongly. In particular, the engine intervention is also intended to prevent the vehicle from tipping over about a vehicle axis oriented in the longitudinal direction of the vehicle.
In a first exemplary embodiment, a change variable describing the time-related change of the transverse acceleration variable is determined as the variable describing the time behavior of the transverse acceleration variable.
The exemplary device according to the present invention includes an apparatus, arrangement or structure which is used to determine a speed variable describing the vehicular speed. The intervention variable is determined as a function of this speed variable, of the transverse acceleration variable, and of the variable describing the time behavior of the transverse acceleration variable. For this end, the exemplary device according to the present invention advantageously has, in the third apparatus, arrangement or structure, a first determining apparatus, arrangement or structure which is used to determine a first value for the intervention variable as a function of the transverse acceleration variable and of the speed variable, and/or a second determining apparatus, arrangement or structure which is used to determine a second value for the intervention variable as a function of the variable describing the time behavior of the transverse acceleration variable and of the speed variable, and/or a third determining apparatus, arrangement or structure which is used to determine an incremental value for the intervention variable as a function of transverse acceleration variable and of the variable describing the time behavior of the transverse acceleration variable. The intervention variable is determined as a function of the first or of the second value and/or of the incremental value.
The three above described determining apparatus, arrangement or structure are implemented as characteristic maps. That is, predetermined values for the intervention variable or the incremental value, respectively, are read out from the respective characteristic maps as a function of the input variables, namely the speed variable and/or transverse acceleration variable and/or the variable describing the time behavior of the transverse acceleration variable. These predetermined variables can be determined in the preliminary stages, for example, on the basis of road tests or by model calculations. The first value of the intervention variable has the character of a static intervention variable since, being determined on the basis of the transverse acceleration variable, it allows for the static behavior of the vehicle. If the first intervention variable is used to influence the throttle-valve position, then the first value of the intervention variable constitutes a static throttle-valve limitation. In a corresponding manner, the second value of the intervention variable constitutes a dynamic throttle-valve limitation since it goes back to the variable describing the time behavior of the transverse acceleration variable. Both values have a limiting character because they are used as intervention variable in the case where, on the basis of the driver""s command, a throttle-valve angle would have to be adjusted which would result in an unstable vehicle behavior in the present vehicle situation. For this reason, a throttlevalve angle which goes back to the first or second value of the intervention variable is adjusted in lieu of the throttle-valve angle which goes back to the driver""s command.
In the case of the influencing of the throttle-valve position, the incremental value has the character of a throttle-valve increase limitation. If, for example, the throttle-valve angle is adjusted according to one of the two values of the intervention variables and the intention is for the throttle-valve angle to be brought near the throttle-valve angle going back to the driver""s command, then the increase in the throttle-valve angle is limited in its increment to produce a smooth increase in the propulsion torque. The incremental value has the same function also in the case in which the throttle-valve position is adjusted according to one of the two values of the intervention variables and the values of the intervention variables increase because of the vehicle behavior.
The use of characteristic maps has the advantage that the intervention variable is continuously determined as a function of the transverse acceleration variable and of the variable describing the time behavior of the transverse acceleration variable.
The first value of the intervention variable advantageously depends on the transverse acceleration variable in such a way that this second value decreases as the value of the transverse acceleration variable increases and/or the first value of the intervention variable depends on the speed variable in such a way that this first value decreases as the value of the speed variable increases. The second value of the intervention variable advantageously depends on the variable describing the time behavior of the transverse acceleration variable in such a way that this second value decreases as the value of the variable describing the time behavior of the transverse acceleration variable increases and/or the second value of the intervention variable depends on the speed variable in such a way that this second value decreases as the value of the speed variable increases. The incremental value of the intervention variable advantageously depends on the transverse acceleration variable in such a way that this incremental value decreases as the value of the transverse acceleration variable increases and/or the incremental value of the intervention variable advantageously depends on the variable describing the time behavior of the transverse acceleration variable in such a way that this incremental value decreases as the value of the variable describing the time behavior of the transverse acceleration variable increases. It is particularly advantageous for the incremental value to assume a very small value, in particular the value zero, first of all, above a predefinable value of the transverse acceleration variable and, secondly, above a predefinable value of the variable describing the time behavior of the transverse acceleration variable.
It has turned out to be advantageous for the absolute value of the transverse acceleration variable and for the absolute value of the variable describing the time behavior of the transverse acceleration variable to be processed in the above mentioned determining apparatus, arrangement or structure. For this reason, the third apparatus, arrangement or structure have a first absolute-value generating apparatus, arrangement or structure which is used to generate the absolute value of the transverse acceleration variable. This absolute value is fed to the first and to the third determining apparatus, arrangement or structure. Moreover, the third apparatus, arrangement or structure has a second absolute-value generating apparatus, arrangement or structure which is used to generate the absolute value of the variable describing the time behavior of the transverse acceleration variable. This absolute value is fed to the second and to the third determining apparatus, arrangement or structure.
The third apparatus, arrangement or structure advantageously has selection apparatus, arrangement or structure which is used to determine a selection variable which has the character of a resulting throttle-valve limitation. The smaller of the two values for the intervention variable is selected as the selection variable. The intervention variable is determined as a function of this selection variable.
This procedure ensures that, at all events, the value of the intervention variable which describes or corresponds to the more critical vehicle condition is taken as the basis for the determination of the intervention variable. If, for example, a vehicle condition has a large transverse acceleration and a small time-related change of the transverse acceleration exists, then the first value determined for the intervention variable is smaller than the second value. Consequently, an engine intervention is required because of the transverse acceleration. The equivalent applies to a vehicle condition in which a small transverse acceleration but a large time-related change of the transverse acceleration exist. By this procedure, the intervention variable is believed to be advantageously limited as a function of the transverse acceleration variable and of the variable describing the time behavior of the transverse acceleration variable to values at which the vehicle behavior is stable.
The device includes an apparatus, arrangement or structure which is used to determine at least a driver command variable describing the driver""s command with regard to the propulsion of the vehicle. This driver command variable is allowed for in the determination of the intervention variable. In particular, the driver command variable is used as the maximum value for the intervention variable. The apparatus, arrangement or structure, which is used to determine the driver command variable, may include, for example, a sensor apparatus, arrangement or structure which is allocated to the accelerator and used for detecting the position of the accelerator.
The driver command variable is believed to be advantageously allowed for in the determination of the intervention variable in such a way that the engine interventions are carried out as a function of the driver command variable as long as the value of the driver command variable is smaller than the selection variable. It is believed that this measure better ensures that the vehicle is not accelerated beyond the driver""s command.
For the determination of the intervention variable, the third apparatus, arrangement or structure have a fourth determining apparatus, arrangement or structure which is used to determine the intervention variable as a function of the selection variable and/or of the incremental value and/or of the driver command variable.
At least the selection variable is determined for consecutive time steps, i.e., it is available in a value-discrete form for discrete time steps. Against the background, the following cases are to be distinguished for the determination of the intervention variable:
if the driver command variable is smaller than the selection variable of the current time step, then the driver command variable is used as the intervention variable and/or
if the driver command variable is greater than the prevailing selection variable, and if the selection variable of the current time step is smaller than or equal to the selection variable of the previous time step, then the selection variable of the current time step is used as the intervention variable and/or
if the driver command variable is greater than the prevailing selection variable, and if the selection variable of the current time step exceeds the selection variable of the previous time step by a predefinable value, in particular by the incremental value, then the intervention variable is derived as the sum of the selection variable of the previous time step and the incremental value and/or
if the driver command variable is greater than the prevailing selection variable, and if the selection variable of the current time step exceeds the selection variable of the previous time step but not by a predefinable value, in particular not by the incremental value, then the selection variable of the current time step is used as the intervention variable.
As already explained, the time-related increase in the intervention variable is believed to be advantageously limited by an incremental value.
Furthermore, it is believed to be advantageous for the intervention variable to be corrected as a function of at least one variable. One approach for this is using, for example, an altitude variable which describes or corresponds to the geographical altitude of the vehicle. This correction takes into account that at greater altitudes, a smaller engine output is available. Applicable is, moreover, a slope variable describing the road gradient in the vehicle""s longitudinal axis. This correction allows for the tractive resistances caused due to the slope. In this connection, moreover, variables can be taken into account as a function of which the intervention variable is corrected to the effect that an equivalent engine torque is adjusted in all operating points of the engine.
The advantageous refinement which is the basis of the first exemplary embodiment can be summarized again as follows: the device for influencing the propulsion of the vehicle includes a first apparatus, arrangement or structure which is used into measure a transverse acceleration variable describing the transverse acceleration acting upon the vehicle. Furthermore, the device contains a second apparatus, arrangement or structure which is used to determine a variable describing the time behavior of the transverse acceleration variable. Moreover, the device has a third apparatus, arrangement or structure which is used to determine a first intervention variable as a function of the transverse acceleration variable as well as a fourth apparatus, arrangement or structure which is used to determine a second intervention variable as a function of the variable describing the time behavior of the transverse acceleration variable. In addition, the device includes a fifth apparatus, arrangement or structure which is used to carry out or perform at least engine interventions for influencing the propulsion, the engine interventions being carried out or performed as a function of the first or of the second intervention variable.
In a second exemplary embodiment, a period duration variable is determined as the variable describing the time behavior of the transverse acceleration variable, the period duration variable describing the time interval of two zero crossings of the transverse acceleration variable with the same sign reversal, in particular with a sign reversal from positive to negative values of the transverse acceleration variable.
It has turned out to be advantageous for the behavior of the vehicle indicating instability or for the previously known behavior of the vehicle to be determined as a function of the amplitude of the transverse acceleration variable and as a function of the period duration of the transverse acceleration variable. This procedure is believed to be particularly suitable for recognizing oscillations in the transverse acceleration variable which may indicate unstable behavior.
For the above reasons, the third apparatus, arrangement or structure advantageously have a first apparatus, arrangement or structure which is used to determine an amplitude variable describing the distance between a minimum value and a maximum value of the transverse acceleration variable within one period of the transverse acceleration variable. If, for example, the transverse acceleration variable exhibits an oscillation, then the minimum value of the amplitude corresponds to a negative half wave, and the maximum value of the amplitude corresponds to a positive half wave. It offers itself to make allowance for the maximum values and minimum values since an unstable vehicle condition shows itself in large fluctuations of the transverse acceleration variable. The intervention variable is determined as a function of this amplitude variable.
Moreover, the third apparatus, arrangement or structure has a second apparatus, arrangement or structure which is used to determine a weighting variable for the intervention variable as a function of the variable describing the time behavior of the transverse acceleration variable and/or of the amplitude variable. In a third apparatus, arrangement or structure which is included in the third apparatus, arrangement or structure described above, the intervention variable is determined as a function of this weighting variable and of a pre-value for the intervention variable, the pre-value depending at least on the driver""s command.
The weighting variable is believed to be advantageously a numerator variable which is incremented, in particular by 1, if the amplitude variable is greater than a threshold value and if the period duration variable lies within a predefinable range of values. The numerator variable is believed to be advantageously limited to a maximum value. Moreover, the numerator variable is reset to a predefined value, in particular to zero, if the amplitude variable is smaller than the threshold value or if the numerator variable lies outside of the predefinable range of values.
Furthermore, it has turned out to be advantageous for the threshold value for the amplitude variable and/or for the range of values for the period duration variable to be predefined as a function of a speed variable describing the vehicular speed. This is useful against the background since the vehicle behavior changes, in terms of instability, to a great extent as a function of the vehicular speed. Thus, an adaptive evaluation is guaranteed.
The zero crossing of the transverse acceleration variable is believed to be advantageously determined as a function of the time-related change of the transverse acceleration variable.
The advantageous refinement which is the basis of the second exemplary embodiment can be summarized again as follows: the device for influencing the propulsion of the vehicle includes a first apparatus, arrangement or structure which is used to measure a transverse acceleration variable describing the transverse acceleration acting upon the vehicle. Furthermore, the device contains a second apparatus, arrangement or structure which is used to determine an indication variable which indicates whether the transverse acceleration variable exhibits a behavior indicating instability or a previously known behavior of the vehicle, in particular an oscillation. Moreover, the device has a third apparatus, arrangement or structure which is used to carry out or perform at least engine interventions for influencing the propulsion, the engine interventions being carried out or performed at least as a function of the indication variable.